Musannaf Ibn Abi Shayba 23:30

Muhammad ibn Sabiq narrated to us, he said: Isra'il narrated to us, from al-A'mash, from Ibrahim, from Alqama, from Abdullah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "The believing person is not one who habitually attacks (others' character), nor one who habitually curses, nor one who is obscene, nor one who is foul-mouthed."